I believe that by "salaried employees" it was meant as "people that have linux kernel programming" in the job description.

Yes, I think you're right. In that case, it certainly wasn't the case back when Linux started. Intel and Redhat are the biggest contributors according to the Linux Kernel Development Report from 2017:

  Intel 10,833 13.1%
  none 6,819 8.2%
  Red Hat 5,965 7.2%

So, "none", although it's the second biggest category, only accounts for 8.2% of contributions.

A lot of kernel developers hide who pays their bills.

Unless they also falsely declare the employers it should not be more than 8.2%

I see, and so you assume that that job would be the contribution.

When I contributed to the kernel (in a rather minor way, I hasten to add), I was competent enough to get a job as a programmer but my job had nothing to do with the kernel. As far as I can remember that was typical for the people who contributed during the first five years or so. I didn't pay much attention after that.

Didn't he mean people paid primarily to develop for Linux, rather than people just developing also developing for Linux?